A comparison of CME-associated atmospheric waves observed in coronal (Fe XII 195 Å) and chromospheric (He I 10830 Å) lines

Although "Moreton" waves have historically been observed in Halpha data, more recently waves have also been observed in chromospheric He I lambda10830 images obtained at the Mauna Loa Solar Observatory. In an effort to better understand the nature of chromospheric waves and their relationship to coronal waves observed in EUV Imaging Telescope (EIT) data, we focus on two events in which waves are observed simultaneously in He I lambda10830 and Fe XII lambda195, lines that are formed in the chromosphere and the corona, respectively. Comparing the waves observed in these two lines allows the determination of the spatial relationship between coronal and chromospheric waves and thus aids in the understanding of the underlying physics of waves in the solar atmosphere. The main goal of this work is to begin an investigation into whether both coronal and chromospheric waves are mechanical (e.g., MHD waves) by looking at their spatial relationship. We find that the chromospheric waves in these two events are cospatial with their coronal counterparts, indicating that they are not mechanical in nature but are chromospheric imprints of mechanical waves propagating through the corona. This conclusion is based on the nature of the formation of the He I absorption line.